Fast Recovering for Network Listening Schemes in Synchronization Over Air for Small Cells

Abstract

The present invention provides methods, apparatuses and a program relating to fast recovering for network listening schemes in synchronization over air for small cells. The present invention includes tracking, at a first base station, a reference signal of a second base station, determining, whether the reference signal can be tracked, if it is determined that the reference signal can be tracked, adjusting, at the first base station, a system clock of the first base station based on the reference signal of the second base station, and estimating and storing parameters relating to a frequency difference between the system clock of the first base station and a system clock of the second base station, and if it is determined that the reference signal cannot be reliably tracked, adjusting the system clock of the first base station based on the stored parameters.

Description

FIELD OF THE INVENTION[0001]The present invention relates to fast recovering for network listening schemes in synchronization over air for small cells. More particularly, the present invention relates to methods, apparatuses and a program relating to fast recovering for network listening schemes in synchronization over air for small cells.BACKGROUND OF THE INVENTION[0002]For LTE (Long Term Evolution) TDD (Time Division Duplex), the inter-cell interferences of eNB (evolved NodeB) to eNB or HeNB (Home eNB) to HeNB and UE (User Equipment) to UE are related to the cell synchronization. In order to overcome the above interferences, strict synchronization is required. The synchronization requirement for a HeNB is defined as the difference in radio frame start timing, measured at the transmit antenna connectors, between the HeNB and any other HeNB or eNB which has overlapping coverage. The synchronization requirement shall be set to 3 μs in all cases, except when the HeNB gets its synchron...

AI Technical Summary

Benefits of technology

[0015]According to the present invention, there are provided methods, apparatuses and a program relating to fast recovering for network listening schemes in synchronization over air for small cells.

Problems solved by technology

For TD-LTE (Time Division-LTE) system, the synchronization technology of small cells is critical because of the DL / UL (Downlink / Uplink) interference issue.

This would cause a restart of the cell and all the UEs inside the cell will be affected.

Therefore, a high frequency of cell search process would result in a very bad user experience.

Practically considering the complex indoor wireless environment and unexpected changes of the environment between neighbouring cells, especially if the small cell is outdoor or in some hot spot, the CRS tracking may fail due to several different reasons:1) the donor cell is off;2) the signal transmission environment between the donor cell and the listening cell is changed permanently so that the listening cell could not find the donor cell.3) the signal transmission environment between the donor cell and the listening cell is changed dynamically due to some temporary interference or shielding source in a short period.

However, when the distance between the two cells is increased up to 20 meters or more across an office room, the CRS tracking was observed to be often dropped for a short while due to the disturbing environment, e.g. caused by walking people in between or the like.

According to the current algorithm described in 3GPP, both of the two schemes will suffer from the frequent restart problem due to the CRS tracking failure in scenario 3 described above.

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